Short answers, pulled from the story.
Xenocrates of Chalcedon was a Greek philosopher and mathematician who led the Platonic Academy from 339/8 to 314/3 BC. He was known for his moral integrity, his doctrine that the soul is a self-moving number, and his attempt to define Platonic philosophy more precisely, often using mathematical elements.
Xenocrates was elected scholarch of the Platonic Academy in 339/8 BC after the departure of Speusippus. He won the vote by a narrow margin, defeating rivals Menedemus of Pyrrha and Heraclides Ponticus.
Xenocrates declined citizenship that was offered to him by Phocion around 322 BC as a reward for his role in negotiating peace with Antipater. He stated that he did not want to become a citizen under a constitution he had struggled to prevent, one that had disenfranchised thousands of poor Athenians.
Xenocrates described the soul as a self-moving number. He held that the soul shares in both permanence and motion by virtue of its dual roots in the same and the different, and that it attains consciousness through the reconciliation of this opposition.
According to Plutarch, Xenocrates attempted to calculate the total number of syllables that could be formed from the letters of the Greek alphabet. His result was 1,002,000,000,000, which may represent the earliest recorded attempt to solve a combinatorial problem involving permutations.
Xenocrates died in 314/3 BC from hitting his head after tripping over a bronze pot in his own house. He was approximately 82 years old at the time of his death.